1. Field of the Invention
The present invention relates to photoresist compositions suitable for lithography using high energy radiation such as a far ultraviolet ray from an eximer laser and the like, electron beam, X-ray or radiated light, and to resins useful as an ingredient of the same compositions.
2. Description of the Related Art
Recently, pattern formation on a quarter micron order has been required with increased high integration of integrated circuits. Eximer laser lithography particularly draws attention since it enables production of the 64 M DRAM and the 256 M DRAM. As a resist suitable for a eximer laser lithography process, a so-called chemical amplification type photoresist utilizing an acid catalyst and a chemical amplification effect is suggested. In a resist film made from a chemical amplification type photoresist, the solubility of irradiated portions in an alkaline developer changes by way of a reaction using an acid as a catalyst, which acid is generated from an acid generating agent in portions irradiated with a radiation. By this reaction, the chemical amplification type photoresist gives a positive type or negative type pattern.
In the production of semiconductor integrated circuits, photolithography is conducted on various substrates. Usually, a photoresist is required to have high transparency against the radiation used for irradiation. However, when lithography is conducted on a substrate having a significantly high reflection ratio against the radiated light, it may be necessary to decrease the transparency of a photoresist to a certain degree in order to avoid unnecessary exposure of the photoresist to the reflected light from the substrate. In this case, a pigment component having a lower molecular weight is usually added to the resist. However, when such a pigment component is added, the basic ability of the resist tends to decrease.